1. Field of the Invention
The present invention relates to a printing apparatus which makes prints with ink.
2. Description of the Related Art
Printing apparatus ink typically is dried at some point in the printing process to avoid streaking or “offsetting,” in which wet ink smears or transfers from one sheet to an adjacent sheet. Japanese Patent Laid-Open No. 2001-71474 discloses an inkjet image forming apparatus provided with a drying unit (i.e., a drying and fixing unit) for drying ink. In the drying unit, heated air is blown onto a sheet surface by an air blowing unit constituted by a heater and a fan. The blown air is collected in an air collecting chamber and is made to recirculate to the air blowing unit.
In the apparatus disclosed in Japanese Patent Laid-Open No. 2001-71474, air is made to circulate through a substantially closed space in the drying unit. When such an apparatus is used for long time continuous printing or high-duty printing with heavy ink consumption, the ink evaporates and generates steam, which stays in a circulation flow path. Thus, humidity in the air in the circulation flow path gradually increases. As humidity increases, dew-point temperature is raised. When sheet temperature is at or below the dew point, condensation occurs on a sheet surface, whereby the sheet becomes harder to dry and moisture content in the sheet increases. Thus, efficiency in drying the sheet decreases.
In addition, when the printing apparatus jams and conveyance of a sheet is stopped in a printing process, an operator should perform an unjamming operation by removing the sheet from the drying unit. However, workability of the operator in such an unjamming operation is not considered in the apparatus disclosed in Japanese Patent Laid-Open No. 2001-71474.